Hi, to hold my mattress in place I have two luggage straps, the ones with the plastic, snap together, buckles; I sewed one to the back side/center of the mattress and screwed the other end to the bed platform. This keeps the bed from sliding to the back of my trailer. The other strap, I sewed to the bottom/foot end of the mattress and screwed the other end of this strap to the bed platform. This keeps the mattress from sliding to the curb side of my trailer. These straps hold the mattress to the night stand and the interior wall at the head of the bed. If I need to remove my mattress, I lift it up slightly and un-fasten the two buckles.
Note: for orientation purposes, my trailer is a rear/sideways queen.